This invention relates to a laser processing apparatus and a laser processing method which are suitable for processing the membrane of a film with a membrane which is used for manufacturing a film capacitor.
One example of a laser processing apparatus of this type is as shown in FIG. 1 (disclosed by Japanese Patent (OPI) No. 35893/1984 (the term "OPI" as used herein means an "unexamined published application").
The laser processing apparatus, as shown in FIG. 1, comprises: a laser oscillator 2 for continuously generating a laser beam L; an optical up collimator for decreasing the divergent angle of the laser beam L and increasing the diameter of the latter L, to provide a parallel laser beam; plane mirrors 4a and 4b for adjusting the direction of advancement of the laser beam L; a polygon mirror 5 for deflecting the laser beam L in a scanning mode; a flat field lens 6 for adjusting the spot size of the laser beam on the irradiation plane; and a cylindrical lens 7 for forming an elliptic laser beam spot.
The laser processing apparatus processes a material 8 as follows: The output laser beam of the laser oscillator 2 is applied to the optical up collimator 3, where the divergent angle of the laser beam L is decreased, and the diameter of the laser beam is increased, to form a parallel laser beam. The output laser beam of the collimator 3 is changed in direction by the plane mirrors 4a and 4b, so that it is applied to a reflecting mirror 5a of the polygon mirror 5. As the polygon mirror 5 rotates, the incident angle of the laser beam L to the reflecting mirror 5a is changed, and accordingly the angle of reflection thereof is also changed. As a result, the laser beam, passing through the flat field lens 6 and the cylindrical lens 7, scans the material 8 being conveyed in the direction of the arrow A (in the direction of conveyance) in such a manner that it goes across the material 8. That is, the laser beam thus applied processes the material in the widthwise direction.
The conventional laser processing apparatus suffers from the following difficulties: The laser beam is deflected only in one direction; that is, it is impossible to process the material 8 with the laser beam longitudinally and laterally; i.e., in the direction of conveyance of the material 8 and in the direction perpendicular thereto simultaneously. Furthermore, in the case where the material 8 is a film on which a membrane is formed, it is difficult for the conventional laser processing apparatus to process it linearly to a width of sub-millimeters.
In addition, with the apparatus, it is impossible to process only the membrane of the film, because the laser oscillator 2 generates the laser beam L continuously.
This difficulty may be overcome by using a Q switch pulse laser oscillator which generates a laser beam in a pulse mode, instead of the laser oscillator 2. In this case, the pulse laser beam is applied to the material 8 as shown in FIG. 2, thus forming a scanning laser beam pattern 10. More specifically, the laser beam pattern is obtained when, while the material 8 to be processed is conveyed in the direction of the arrow B, the Q switch pulse laser beam L is applied thereto in a scanning mode, that is, the pulse laser beam L elliptic in section (as indicated at 10a) is applied successively in a direction D which forms an angle (n) with the direction C which is perpendicular to the direction of the arrow B.
In the scanning laser beam applying method using the laser processing apparatus as described above, in processing the material 8 in a direction perpendicular to the direction of conveyance with the pulse laser beam L forming the elliptic pattern 10a, the direction of the major diameter of the elliptic pattern 10a is in parallel with the aforementioned direction C. Therefore, the elliptic patterns 10a are arranged in the form of a staircase on the material, so that the resultant laser-processed line is not uniform in the processing direction.
One example of the laser processing apparatus of this type is a pattern forming device using a laser beam (disclosed by Japanese Patent Application (OPI) No. 94482/1982).
The pattern forming device 21, as shown in FIG. 3, comprises: a convex lens 23 for increasing the diameter of a laser beam 22a circular in section which is outputted by a laser oscillator (not shown), thus providing a laser beam 22b; a convex lens 24 for converting the laser beam 22b into a parallel laser beam 22c; a cylindrical lens for converting the parallel laser beam 22c into a laser beam 22d elliptic in section; and a cylindrical lens 26 for converting the laser beam 22d into a parallel laser beam 22e elliptic in section. That is, the pattern forming device 21 operates to convert the laser beam 22a circular in section into the laser beam 22e elliptic in section.
The pattern forming device thus constructed is disadvantageous in the following points: It suffers from a difficulty that, whenever it is required to change the configuration of the laser beam 22a which is circular in section and generated by the laser oscillator, thereby to change the laser processing diameter (or to change the laser processing width), it is necessary to replace some of the lenses 23, 24, 25 and 26 to reconstruct the optical system. In addition, when deflecting the laser beam in a scanning mode with a polygon mirror as a reflecting optical system, it is impossible to change the width of the laser beam thereby to change the linear laser processing width into a desired one.
Sometimes, it is required to process a material having a membrane with the laser processing apparatus as follows: That is, it is required to process only the membrane of the material with the laser beam. In this case, heretofore the laser processing operation is carried out with the membrane facing the laser beam.
In this case, the following difficulties are involved: During application of the laser beam, the material being processed is partially scattered, or evaporated, thus damaging itself. This difficulty may be eliminated by the provision of dust absorbing means. However, in this case, the dust absorbing means should not interfere with laser beam applying means and the laser beam path, with the result that the laser processing apparatus is intricate in construction.